Method for handling injection molded articles

ABSTRACT

A method and apparatus for handling preforms from an injection molding machine whereby an array of molded articles received from the mold is reconfigured into a single row to assist in downstream auxiliary processing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/280,080, filed Oct. 25, 2002, which is a continuation-in-part ofco-pending application Ser. No. 09/877,680, filed Jun. 8, 2001 (nowabandoned), which claims the benefit of U.S. application No. 60/267,859,filed Feb. 9, 2001. The entire text of the above-referenced disclosureis specifically incorporated by reference herein without disclaimer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the handling of injection moldedarticles. More particularly, the invention relates to a method andapparatus for handling injection molded articles of substantiallyamorphous polyethylene terephthalate and similar materials, whereby anarray of molded articles is reconfigured into a single row.

2. Summary of the Prior Art

The use of polyethylene terephthalate (hereinafter referred to as “PET”)and similar materials as the materials of choice in the formation ofnumerous injection molded articles is well known in the art. Forexample, in the bottle and container industry, the blow molding ofinjection molded PET preforms has gained wide acceptance, and isexperiencing strong growth. Among the reasons for this is the fact thatPET and similar materials offer a wide range of desirable properties.Specifically, PET materials generally evidence high strength, goodclarity, and low gas permeation characteristics. Further, PET materialsare comparatively easy to recycle. Accordingly, they are desirable foruse in retail packaging applications.

In systems and apparatus for the injection molding of articles/preformsof the type alluded to above, a mold and a molten material transportmeans are commonly provided. The mold typically includes a first cavityextending inwardly from an outer surface of the mold to an inner end, anarticle formation cavity, and a gate connecting the first cavity to thearticle formation cavity. The gate defines an inlet orifice in the innerend of the first cavity, and an outlet orifice which opens into thearticle formation cavity.

SUMMARY OF THE INVENTION

The primary aspect of the invention is to provide a product handlingdevice having a serpentine channel having a first end and an outlet endin which sections thereof correspond to an arrangement of an array ofmolding cores of an injection mold, the serpentine channel definedwithin a plate and arranged to receive, in use, preforms presentedthereto in a pattern of said array. The device further includes a drivemechanism positioned relative to the channel, the drive mechanismincluding drive means arranged to advance preforms, located in usewithin the serpentine channel, towards the outlet end, whereby preformsegress from outlet end of the channel as a single row of preforms.

Another aspect of the present invention relates to a method ofconverting a two-dimensional array of preforms into a one dimensionalrow of preforms in a singulator having a serpentine channel, the methodcomprising the steps of placing the two-dimensional array of preformsinto corresponding sections of the serpentine channel, engaging thepreforms with a mechanically driven drive member to urge the preformsthrough the serpentine channel, and from an outlet of the serpentinechannel egressing the preforms from the singulator as a row of preforms.

The foregoing is achieved by providing an injection molding machinewhich comprises a plurality of preform mold cavities for the formationof molded articles therein. Following the molding process, the preformsare placed in the singulator so that each preform may be passed inline,and alternatively subjected to further processing by such devices aslaser cutting of an elongated gate vestige, or automated preforminspection, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified isometric view of an injection molding machinebase in accordance with the present invention.

FIG. 1B is a simplified operator side view of an injection moldingmachine in accordance with the present invention.

FIG. 2 is an isometric view of the underside of the shuttle table inaccordance with the present invention.

FIG. 3 is an enlarged isometric view of the laser cutting station withan array of preforms.

FIG. 4 is a partial detail view of the laser cutting station.

FIG. 5 is a detailed cross-sectional view of a typical preform.

FIG. 6 is a top plan view of the laser system layout.

FIG. 7 is an isometric view of the topside of the singulator inaccordance with the present invention.

FIG. 8 is an isometric view of the topside of the singulator inaccordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 5 which shows a blank 108, also termed preform,of a substantially amorphous thermoplastic material, preferably PET,having a mouth portion 122, a substantially conical portion 124extending from the mouth portion, a substantially cylindrical portion126, and a region of material 128 which, when forming the blank 108 intoa container, forms the bottom of the container. The blank 108 has acentral cavity 130 with a substantially cylindrical upper portion 132and a substantially cylindrical lower portion 134, whose circumferenceis smaller than that of the upper portion 132. The transition betweenthe upper and lower portions 132, 134 of the central cavity is asubstantially conical transition portion 136. The cylindrical lowerportion 134 is closed at its bottom, which is bulging outwards andcomprises an elongated vestige or sprue 109. It is this elongatedvestige 109 that will be severed from the preform 108 because itexhibits high crystallinity.

The preform 108 thus serves as starting material in the making of ablow-molded container for example a reusable bottle for beverages.

The mouth portion 122 has a threaded portion 138 and an annular grippingportion 140. The material forming the mouth portion 122 is designated Ain FIG. 5. The conical portion 124 encloses the substantiallycylindrical upper portion 132 of the central cavity of the blank 108.The cone of the conical portion 124 results from an increase of thethickness of this portion towards the bottom of the blank 108. Thematerial of the blank 108 forming the conical portion 124 is designatedB in FIG. 5.

The proximal part, with respect to the bottom of the blank 108, of thesubstantially cylindrical upper portion 132 of the cavity 130 is definedby a wall having a substantially uniform wall thickness in all parts ofthe cylindrical portion 126. The region of the substantially cylindricalportion is marked C in FIG. 5.

The region of material 128, which after reshaping of the blank 108 isintended to constitute the bottom of the container, has an increasedwall thickness in the region of the transition portion 136 of the cavityof the blank 108, and maintains this wall thickness substantiallythroughout the entire region of the substantially cylindrical lowerportion 134 of the cavity. The wall thickness of the blank 108thereafter decreases in the closed bottom of the blank to have itsminimum thickness in a central region of material 142 in the bottom ofthe blank 108. Reference D indicates the material of the blank 108 whichin the resulting container is reshaped to form part of the bottom of thecontainer, while reference E indicates the material of the blank 108which substantially retains its shape when forming the container.

Referring now to FIGS. 1A and 1B, an injection molding system 10according to the present invention is generally shown. The injectionmolding system 10 is comprised of an injection molding machine 12, atransport subsystem 14, a pick and place robot 16, a laser cuttingstation 18 and an inspection station (not shown). All of thesesubsystems work together to form a high speed manufacturing process forthe production of injection molded articles, for example PET preforms108.

In the preferred embodiment, the injection molding machine 12 is anindex type machine with a rotary turret 36 for the production of PETpreforms 108. As one skilled in the art will recognize however, any typeinjection molding machine may easily be adapted for use with the presentinvention.

Injection molding machine 10 generally includes a rotary turret 36 witha plurality of movable mold halves 37 a-37 d, a stationary mold half andplaten 34 and injection unit 32, all positioned on base 30.

Injection molding system 10 may be used for molding a variety ofdifferent types of articles and accordingly, is not limited for use withany particular type of article. Preforms are referred to throughout thisdescription by way of example only.

While the rotary turret 36 is shown throughout this description asrotatable on a horizontal axis, and this is the preferred embodiment, itis feasible that a similar design of a movable turret block providingthe clamping action may be provided which is rotatable on a verticalaxis. Accordingly, this invention is not considered limited to thehorizontal axis feature.

As shown in FIG. 1B, rotary turret 36 is preferably longitudinallymovable on base 30 via a set of bearings blocks 43 attached to thebottom of a pair of turret fittings (not shown). Base 30 includes linearbearings 44 which engage bearing blocks 43 and counteract upward forcesand tipping forces that may act on the turret block assembly. Rotaryturret 36 is rotatable preferably by a rotational drive (not shown) incommunication with belts and pulleys, preferably an electric servo drivemotor and preferably on a horizontal axis H through arcuate sectorspreferably of substantially 90 degrees. Preferably, the rotational driveis connected via a belt drive (not shown) to axis (not shown) forrotating the rotary turret 36, as shown in FIG. B, while the electricservo drive motor is preferably mounted on one of turret fittings (notshown) extending from base 30.

As shown in FIG. 1B, rotary turret 36 includes a plurality of movablemold halves, i.e., movable mold halves 37 a-37 d each of which includesa plurality of mold cores 45 a-45 d, respectively, each set having atleast one mold core, adapted for engagement with a set of mold cavities40, each set including at least one mold cavity and located instationary mold half and platen 34. Preferably, four movable mold halvesor faces 37 a-37 d are provided on rotary turret 36, although any numbersupportable by the size of the rotary turret 36 can be used. Sets ofmold cores 45 a-45 d are adapted to be rotated into horizontal andvertical alignment with sets of mold cavities 40.

Referring still to FIGS. 1A and 1B, rotary turret 36 includes sets ofejector pistons or stripper rings (not shown), and a system for theoperation thereof, which operate on sets of mold cores 45 a-45 d andstrippers positioned on movable mold halves 37 a-37 d, respectively.Accordingly, sets of ejector pistons or stripper rings (not shown) arepositioned within rotary turret 36 and parallel to sets of mold cores 45a-45 d and perform the function of stripping the mold cores of finishedmolded articles, for example, preforms, such as those shown in FIGS. 4and 5. Each movable mold half 37 a-37 d and platen 34 includes at leastone ejector piston in each set (not shown) for stripping finishedarticles from sets of mold cores 45 a-45 d. For the detailed design ofthe ejector piston or stripper ring system for use with sets (notshown), reference is made to U.S. Pat. No. 5,383,780, issued Jun. 24,1995, to the assignee of the present invention, for incorporation byreference of a design of the ejector piston or stripper ring system,particularly column 4, line 29, to column 7, line 6, and FIGS. 1-8.Preferably, the ejector piston or stripper ring system is actuated viathe hydraulic services supplied to the rotary turret 36, as discussedbelow. The hydraulically actuated ejector piston or stripper ring systemactuated by on board hydraulic services is the preferred design,however, other designs may be used.

Rotary turret 36 is movable backward and forward along linear bearings44 on base 30 via piston/cylinder assemblies 38 positioned in stationarymold half and platen 34, as shown in FIG. 1B. Preferably fourpiston/cylinder assemblies 38, as shown in FIG. 1B are used which arepositioned in the corners of stationary mold half or platen 34. Eachpiston/cylinder assembly 38 is attached to tie bars 47, respectively,which tie bar 47 acts as the piston shaft. Accordingly, tie bars 47extend from the piston/cylinder assemblies 38 and are connected at anopposite end to rotary turret 36. In order to move rotary turret 36backward and forward relative stationary mold half and platen 34,pressurized fluid is forced into cylinders assemblies 38. The side ofthe cylinder assemblies 38 in which pressurized fluid is forced against,determines the direction in which rotary turret 36 moves relativestationary mold half and platen 34, that is, either into an open orclosed position. Tie bars 47 pass through the turret fittings 46 and areattached thereto via retaining nuts.

Services, not shown in FIG. 1B, are provided to rotary turret 36 via arotary union 31. Accordingly, as rotary turret 36 rotates, services arecontinuously supplied to the movable mold halves 37 a-37 d. Suchservices include the supply of electricity, pressurized fluid, coolingfluids, and hydraulic fluids, etc. For using these services, rotaryturret 36 also includes the required circuitry and control valves (notshown) on board and movable and rotatable with the turret block.

Injection unit 32, preferably in the form of a reciprocating screwinjection unit, is connected with stationary mold half and platen 34positioned on base 30 for providing melt to the mold cores for molding.Injection unit 32 is preferably movable into and out of engagement withstationary mold half and platen 34 by means of carriage cylinders (notshown) on rollers and hardened ways, similar to as described above foruse with rotary turret 36.

Still referring to FIGS. 1A and 1B, the transport subsystem 14 comprisesan inside and outside track 48 a and 48 b mounted to the base 30 andrunning from under the rotary turret 36 to a position of easy access bythe pick and place robot 16. A motor 50 is attached to one end of theinside track 48 a which is in communication with a shaft 54 which runsbetween the inside and outside track 48 a and 48 b. Attached at each endof the shaft 54 is a pair of belts 52 which run the entire length of thetracks 48 a and 48 b. Attached to the inside surface of each track 48 aand 48 b is a second pair of linear bearings 56 which interface with aplurality of bearing blocks 60 (FIG. 2) rigidly affixed to a shuttletable 58. Each belt 52 is attached to the shuttle table 58 such that theshuttle table 58 is operatively positioned (back and forth) through theuse of the motor 50 along tracks 48 a and 48 b. In this arrangement, theshuttle table is controllably positioned beneath the rotary turret 36 toaccept the molded preform 108. Once the shuttle table 58 is filled withpreforms 108, it is operatively positioned at a far end of the tracks 48a and 48 b for easy access by the pick and place robot 16.

Referring now to FIG. 2, the shuttle table 58 comprises a horizontalsurface 62 with a plurality of holes 64 arranged to interface with themovable mold halves 37 a-37 d of the rotary turret 36. Inserted in eachhole 64 is a spacer 66 sized to accept the molded preform 108. In thepreferred embodiment, the spacers are made from a soft plastic materialto minimize the scratching of the preform 108 that may occur during thehandoffs from the shuttle table 58.

In the preferred embodiment, the shuttle table 58 must translateupwardly to interface with and catch the plurality of molded preforms108 when they are released by the rotary turret 36. To accomplish thismotion, a servo-motor 68 is mounted beneath the horizontal surface 62and in communication with a pair of ball screws 70. Each ball screw 70is attached to opposite ends of the horizontal surface 62 and groundedto an inside and outside support 74 a and 74 b. A second belt 72 runsbetween the ball screws 70 such that the servo-motor 68 controls bothball screws 70 for raising and lowering the horizontal surface 62 of theshuttle table 58.

Once the shuttle table 58 has received a plurality of preforms 108, thetable 58 moves away from the injection molding machine 12 and alignswith the robot 16. The robot 16 comprises a frame 80 which carries apick-up table 84 along a trackway 82. The pickup table 84 interfaceswith the shuttle table 58 with a plurality of air operated fingers 86which are inserted into each preform 108. The pick up table 84 is movedunder precise control in a manner similar to the way the shuttle table58 is moved and therefore won't be further described herein. In thepreferred embodiment, once the air operated fingers 86 are positionedinside the preforms 108, air is communicated to the fingers 86, causingthem to expand and grab on the inside surface of the preforms 108. Thereare myriad methods for picking up the preforms 108, and the forgoing isjust an example of one of these methods and should not be read to limitthe scope of the invention.

Once the plurality of preforms 108 in the form of an array are retrievedby the pick up table 84, the table translates to a distal location sothat the preforms are aligned with a singulator 88. The singulator 88 ofFIG. 1A is shown in more detail in FIG. 7, as having a flat plate 200with a continuous serpentine groove 89 machined therein, the plate 200is preferably made from Derlin™ (a polyoxymethlene made by Dupont). Thepitch between straight parallel sections of the serpentine channelcorresponds to a pitch between columns in a mold plate. The serpentinegroove 89 is designed to accept a plurality of different preform sizes.Once the preforms 108 are properly seated in the groove 89 by the pickup table 84 (FIG. 1A), the air in the fingers 86 (FIG. 1A) is removedand the plurality of preforms 108 are released into the groove 89. Thearray of preforms may also be delivered thereto by other equivalentdevice to the pickup table 84 such as an end-of-arm-tool on a robot. Theserpentine channel 850 is dimensioned such that an annular grippingportion 140, formed in the molded article, is too large to slip into theserpentine channel, i.e., the annular gripping portion of the preformrests on an upper surface 200 of the singulator. The singulator 88further includes a drive chain 202 driven by a drive motor 204. Thedrive chain can, for example, be either of a rubber construction or alinked construction. The drive chain 202 is a continuous drive chainthat is linked to the drive motor 204 through at least one sprocket 208or the like. The drive chain therefore follows the serpentine channel 89along a substantial proportion (if not the entire length of) its paththrough the plate 200. Guides 210 and free-rotating sprockets 206 definea path of the drive chain adjacent to the serpentine channel. In orderto advance preforms located in the serpentine channel 89, drive members(such as paddles) 212 are coupled to the drive chain 202, such drivepaddles preferably being of a plastic material with some limited elasticproperties. The drive paddles 212 extend across the surface of theserpentine channel 89. The drive paddles therefore engage against a neckor upper surface of the preform to urge, under the control of the motordrive 204, the array of preforms along the serpentine channel 89 andinto a linear row of preforms that egress from the singulator 88 andinto the conveyor 90 (FIG. 1A) and are moved onwards for furtherhandling or processing. The drive chain can include one or more drivepaddles 212. In operation, the drive motor is preferably intermittentstop-start mode and is controlled using feedback from proximity sensors216 mounted to the plate 200 and proximity targets mounted to the drivensprocket 208.

Reference is now made to FIG. 8 in which an alternative embodiment ofthe singulator 88 of FIG. 1A is shown. The singulator 88, previouslydescribed as a flat plate 840 containing a continuous serpentine channel850, may be made from a machined plate of steel or aluminum or,alternatively, it can be constructed in a box-like fashion. Theserpentine channel is configured to receive an array of preformsdelivered thereto by the pick-up table 84 or other equivalent device,such as an end-of-arm-tool on a robot. In other words, a pitch betweenstraight parallel sections of the serpentine channel corresponds to apitch between columns in a mold plate. The serpentine channel 850 isdimensioned such that a annular gripping portion 140, formed in themolded article, is too large to slip into the serpentine channel, i.e.,the annular gripping portion of the preform rests on an upper surface864 of the singulator. It is preferably that the majority of the bodyportion of the preform is contained within the channel. The singulator88 further includes a drive chain 866 driven by a drive motor 868. Thedrive chain can, for example, be either of a rubber construction or alinked construction. The drive chain 868 is a continuous drive chainthat is linked to the drive motor 868 through at least one sprocket 870or the like. The drive chain therefore follows the serpentine channel850 along a substantial proportion (if not the entire length of) itspath through the plate 840. Rollers, small free-rotating sprockets 872define a path of the drive chain adjacent to the serpentine channel. Inorder to advance preforms located in the serpentine channel 850, drivemembers (such as paddles) 874 are coupled to the drive chain 866, suchdrive paddles preferably being of an plastic material with some limitedelastic properties. The drive paddles 874 extend across the surface ofthe serpentine channel 850. The drive paddles therefore engage against aneck or upper surface of the preform to urge, under the control of themotor drive 868, the array of preforms along the serpentine channel 850and into a linear row of preforms that egress from the singulator 88 andare moved onwards for further handling or processing, preferably, by aconveyor system (not shown) coupled to an outlet 876 of the singulator88. The drive chain can include one or more drive paddles 874. Thesingulator 88 may include a heat sink or other cooling system 880 (e.g.,a water-cooled system including channels or piping 882 located throughthe singulator 88).

Although the drive chain 866 is shown to be on the surface 864 of thesingulator 88, it may also be included beneath the surface should abox-like construction be employed. Indeed, internal mounting may bepreferably from a safety handling perspective.

Referring to FIGS. 3 and 4, the preforms 108 travel down the conveyor 90to the laser cutting station 18. The laser cutting station 18 comprisesa rotary track 92 which accepts the preforms from the conveyor 90 andspins them in a circular fashion past a plurality of laser beams 103.The rotary track 92 comprises a circular holder 96 with a plurality ofpockets to accept the preforms 108 from the conveyor 90. The rotationalspeed of the rotary track 92 is matched with the linear speed of theconveyor 90 so that preforms 108 are quickly and easily transferred intothe pockets of the circular holder 96. As the rotary track 92 rotates(and before the preform aligns with the first laser beam 103), asegmented top plate 94 is lowered into contact with the top surface ofthe preform 108 and forces the bottom of the preform 108 to interfacewith a lower shield 98. In this arrangement, the elongated vestige 109is now properly aligned with the plurality of laser beams 103 as theytravel around with the rotary track 92. The elongated vestige 109travels past each laser beam 103 in rapid succession, thereby severingthe vestige 109 from the preform 108. The now severed vestige 109 dropsinto a reclamation bin 112, where the vestige 109 will be laterre-melted and recycled.

The shield 98 is specifically designed to both protect the main body ofthe preform 108 from damage by the laser and also maintain a givenlength of remaining vestige. Testing has shown that without the shield98, energy from the laser 102 can cause inadvertent damage to the bodyof the preform 108. In addition, international quality inspectioncriteria dictate the required length of any remaining vestige. Using theshield 98 insures the laser cuts the elongated vestige 109 at the properlocation.

Referring to FIG. 6, the various optical components which comprise thelaser cutting setup are generally shown. Two lasers 102 are each alignedsuch that the laser beam passes first through a splitter 106 a and 106 brespectively. The splitters 106 a and 106 b are designed to reflect halfof the laser beam power at 90 degrees from the entering beam, and allowthe other half of the laser beam power to continue on to a mirror 118 aand 118 b where the remaining laser beam power is also reflected at 90degrees from the entering beam. In the preferred embodiment, the optimumlaser cutting set up was found to be two 500 W CO₂ lasers focused inlinewith the elongated vestige 109. In this arrangement, four laser beams,each with approximately 250 watts of power are transmitted to a bank offocusing lenses 104 a-104 d. Positioners 120 a-120 d are attached toeach lens 104 and allow for minute adjustments to the focused laser beamfor machine set.

A by-product of the laser cut is a very fine dust which tends toaccumulate on the outside surface of the preform. To remove this dust, abrush 115 is mounted in the path of the preforms 108 as it passes to anunload conveyor 116. Alternatively, or in combination, forced air couldbe blown over the preforms as the cut is made, or an electrical chargecould be placed on the preforms to repel the flying plastic dust.

The unload conveyor 116 accepts the preforms 108 in a linear fashionafter they have been cut and transfers them to an inspection station(not shown) where each preform is inspected for compliance with qualitycontrol standards.

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modification of form, size, arrangement of parts anddetails of operation. The invention rather is intended to encompass allsuch modifications which are within its spirit and scope as defined bythe claims.

1. A method of converting a two-dimensional array of injection moldedpreforms into a one dimensional row of preforms in a singulator having aserpentine channel, the method comprising: placing the two-dimensionalarray of preforms into corresponding sections of the serpentine channel;engaging the preforms with a mechanically driven drive member to urgethe preforms through the serpentine channel; and from an outlet of theserpentine channel, egressing the preforms from the singulator as a rowof preforms.
 2. The method of claim 1, wherein the singulator includes aheat sink.